The present invention relates to a disc cartridge for encasing a recording medium such as an optical disc or a magnetic disc.
In general, a magnetic disc or an optical disc is encased in a cassette case made of two shell halves. A hole into which a spindle for rotating the disc is to be inserted is formed in a central portion of the cassette case. Head insertion holes into which a write and read head is to be inserted is formed in the cassette case so as to extend in the radial direction to traverse the recording surface of the disc.
Such a disc cartridge is shown in, for example, Japanese Utility Model Unexamined Publication No. 62-168176. This cartridge has a shell for encasing the disc. A spindle hole is formed in the central portion of the shell half. A hub formed in the central portion of the disc is located in the spindle hole of each shell half. The spindle of the recording and reproducing apparatus is to be located at the hub which is sucked by a turntable.
The head insertion holes are formed on an insertion side of the cartridge relative to the recording and reproducing apparatus. A write and read head (pickup head) is inserted into one of the head insertion holes. The head insertion holes are closed and opened by sliding movement of the shutter.
The shutter is bent at its intermediate portion so as to extend to the top and bottom of the cartridge to cover the head insertion holes and two spindle holes. On the insertion side of the cartridge into the recording and reproducing apparatus, the shutter is slidingly moved along a guide portion of the cartridge front edge to open and close the insertion holes and the spindle holes.
However, it is general that the shutter is made of metal, whereas the cartridge is made of plastic. Therefore, when the shutter is frequently moved on and along the cartridge, frictional or abraded chips are generated due to the sliding movement between the metal and plastic. The chips would enter through the openings of the cartridge into the interior thereof to stick or adhere to the disc.
Also, the sliding movement of the shutter of the conventional cartridge is not smooth, which would lead non-smooth sliding contact between the shell and the shutter.